Method for surface preparation of solid substances and surface-prepared solid substances

ABSTRACT

A method for modifying the surface of a solid material and a surface-modified solid material are provided, where an excellent adhesion strength between the surface of the solid material and any of coating films made of various UV-curing resins or the like can be obtained. In other words, it is attained by carrying out a silicatizing flame treatment on the surface of the solid material by wholly or partially blowing a flame of a fuel gas containing a specific silicon-containing compound having a flash point of 0 to 100° C. and a boiling point of 105 to 250° C., such as hexamethyldisilazane, vinyltrimethoxysilane, trifuloropropyl trimethoxysilane, 3-chloropropyl trimethoxysilane and the like.

TECHNICAL FIELD

The present invention relates to a method for modifying the surface of asolid material and a surface-modified solid material. More specifically,the present invention relates to a method for modifying the surface of asolid material, which can exert an excellent modifying effect on anycoating film made of any kind of a UV-hardening resin or the like and toa surface-modified solid material obtained by such a method.

BACKGROUND TECHNOLOGY

Many of films or molded products made of solid materials, such assilicone rubber, fluorine-containing rubber, and polyethylene resin,have hydrophobic or water-repellent surfaces, so that they can beusually difficult to be attached to other members or to be subjected tosurface treatments including adhesion printing and UV-coating. Inaddition, solid materials having metallic surfaces made of metals suchas stainless steel and magnesium have problems in that they have thepoor adhesion strength and surface-smoothness in comparing with theother metals. Therefore, when a UV-curing type coating material or thelike is directly applied on such a surface, the resulting coating filmmay be easily peeled off. Furthermore, other attempts including theaddition of inorganic particles, such as those of titanium oxide andzirconium oxide, as a photocatalyst to a polymer material have beenconducted in the art. However, there is a problem in that the particleshave poor dispersability and are difficult in handling.

Therefore, as a method for improving the surface characteristics of thesolid material, for example, the surface thereof may be subjected to aprimer treatment or coated with a silane-coupling agent or atitanium-coupling agent dissolved in a solvent.

However, for attaining a desired modifying effect, these conventionalmethods have some problems in manufacturing steps. For instance, acomparatively large amount of the primer or silane-coupling agent or thelike should be required, while consuming much processing time.

Therefore, as an alternative for the primer treatment and thecoupling-agent treatment, the methods to be used for improving thesurface characteristics of solid materials include a UV-irradiationmethod, a corona-discharge treatment, a plasma treatment, a method forproviding the surface with a functional group, a surface light graftingmethod, a sandblasting treatment, a solvent treatment, and an acidcromic mixture treatment.

For instance, in JP 5-68934 A, there is disclosed a technology forimprovements in wettability and adhesiveness of coating by UVirradiation with a high pressure mercury lamp fabricated from syntheticquartz. Further, U.S. Pat. No. 5,098,618 discloses a method forimproving the wettability and adhesiveness of coating by selectivelyirradiating UV light of 185 nm and 254 nm in wavelength onto the surfaceof hydrophobic plastics under mixed gas. Also, JP 10-67869 A discloses amethod of corona treatment by blowing the gaseous material as well asapplying high voltage pulse to the surface of the plastic materialshaving the low wettability. Furthermore, JP 8-109228 A discloses amethod for graft polymerization of a vinyl monomer on the surface of apolyolefin resin or the like after carrying out a surface-activationtreatment, such as an ozone treatment, a plasma treatment, a coronatreatment, a high-voltage discharging treatment, and a UV irradiationmethod, on that surface in order to improve dye-affinity.

However, these surface-modification methods cause not only insufficientimprovements on surface characteristics but also various other problemsincluding: environmental problems such as contaminated and dangerousworking surroundings; work-related problems such as the necessity ofwashing and waste liquid treatment; and economical problems such aslarge-scaled and expensive facilities.

On the other hand, as a simple and cheap method for modifying thesurface of a solid material, a prolonged flame treatment on the surfaceof the solid material may be suggested. However, according to themethod, the modification of the surface of the solid material, typicallywettability and contact-angle characteristics, is insufficient and aproblem that the modifying effect of the method cannot last for along-term exists. Further, as disclosed in JP 9-124810 A, in case ofapplying the flame treatment onto the surface of the solid material fora long time, a problem that thermal deformation is easily caused exists.

Under the circumstances, DE 0019926 A1 discloses a method for modifyingthe surface of a solid substrate mainly provided as a metal or glassarticle, which comprises the steps of: modifying the surface of thesolid substrate by at least one oxidizing flame; and modifying thesurface of the solid substrate by at least one silicatizing flame.According to the method for modifying the surface of the solidsubstrate, the surface of the solid substrate may be modified securelyand an ink for printing, paint for UV curing and the like may be made toadhere securely.

However, since the modification method disclosed in DE 0019926 Al usesalkoxysilane alone as a silicon-containing compound, such astetramethoxysilane (boiling point: 121° C., flash point: 22° C.), thereis a problem in that a stable modifying effect cannot be obtained for acoating film made of any of various UV-curing resins. Besides, there isanother problem in that alkoxysilane compounds have high activity andtends to hydrolyze a general-purpose resin such as polycarbonate.Furthermore, there is another problem in that, since the method alsocontains an additional oxidizing flame treatment prior to thesilicatizing flame treatment, it takes a long time as a whole to carryout these treatments even though a superior modifying effect may beobtained.

Furthermore, JP 2001-500552 A discloses a flame-treatment method formodifying the surface of a polymer substrate. In other words, theflame-treatment method disclosed comprises the step of exposing thepolymer substrate to a flame with a combustion aid, a mixture of a fueland an oxidizing reagent, which contains hexamethyldisiloxane (boilingpoint: 100 to 101° C., flash point: −1° C.) as a silicon-containingcompound.

However, since the method disclosed in JP 2001-500552 A useshexamethyldisiloxane as a silicon-containing compound, there is aproblem in that a stable modifying effect cannot be obtained for acoating film made of any of various UV-curing resins including an epoxyacrylate-based UV-curing resin, an urethaneacrylate-based UV-curingresin, and a polyester acrylate-based UV-curing resin. Besides, themodifying effect due to hexamethyldisiloxane may decline comparativelywithin a short time.

The present inventors, as a result of their concentrated efforts, havecompleted the present invention by finding out that, by carrying out asilicatizing flame treatment on the surface of a solid material, a metalmaterial, or the like using a silicon-containing compound having both aspecific boiling point and a specific flash point, an excellentmodifying effect can be exerted for a coating film made of any of a widevariety of UV-curing resins or the like and the surface of a solidmaterial or the like can be uniformly modified in a sufficient mannereven if the step of oxidizing flame treatment is omitted.

In other words, the present invention provides a method for modifyingthe surface of a solid material and a surface-modified solid material,where the surface of the solid material such as a metal material ismodified by efficiently carrying out a silicatizing flame with asilicon-containing compound, thereby exerting an excellent modifyingeffect even on a coating film made of any of various UV-curing resins orthe like.

SUMMARY OF THE INVENTION

[1] According to an aspect of the present invention, the above-mentionedproblems can be solved by providing a method for modifying the surfaceof a sold material, where the surface of the solid material is wholly orpartially blow treated with a flame of a fuel gas that comprises asilicon-containing compound having a flash point of 0 to 100° C. and aboiling point of 105 to 250° C.

In other words, both the flash point and the boiling point of thesilicon-containing compound are limited within predetermined ranges,respectively. In addition, the silicon-containing compounds, which canbe used in the present invention, include hexamethyl disilazane, vinyltrimethoxy silane, vinyl triethoxy silane, trifluoropropyltrimethoxysilane, trifluoro propyl trichlorosilane, 3-aminopropyltrimethoxysilane, 3-aminopropyl triethoxysilane, and 3-chloropropylmethoxysilane, which may be used independently or in combination of twoor more of them. Such a silicon-containing compound allows the surfaceof the solid material to be uniformly modified. Besides, due to therelationship of the flash point and the boiling point of thesilicon-containing compound, the silicon-containing compound partiallyremains on the surface of the sold material. Therefore, an excellentadhesion strength can be obtained between the solid material and thecoating film made of any of materials including an epoxyacrylate-basedUV-curing resin, an urethaneacrylate-based UV-curing resin, and apolyesteracrylate-based UV-curing resin.

[2] Another aspect of the present invention is a surface-modified solidmaterial having a wetting index (measured at 25° C.) in the range of 40to 80dyn/cm attained by wholly or partially blowing the surface of asolid material with a flame of a fuel gas that comprises asilicon-containing compound having a flash point of 0 to 100° C. and aboiling point of 105 to 250° C.

Such a configuration of the surface-modified solid material allows toprovide a solid material on which a coating film having an extremrelyexcellent adhesion strength without paying too much attention onchoosing one from various UV-curing paints can be formed in addition toan adhesive generally used in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structure of a surface modification apparatus ofthe present invention.

FIG. 2 illustrates the blow treatment process by flame with a surfacemodification apparatus of the present invention.

FIG. 3 illustrates the structure of a portable surface modificationapparatus of the present invention.

FIG. 4 illustrates the flame blow treatment (1).

FIG. 5 illustrates the flame blow treatment (2).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, with reference to the figures, embodiments regarding themethod for modifying the surface of a solid material, thesurface-modified solid material, and the apparatus for modifying thesurface of a solid material of the present invention will be explainedin detail.

First Embodiment

The first embodiment is a method for modifying a surface of a solidmaterial wherein the surface of the solid material is subjected tosilicatizing flame treatment such that the surface of the solid materialis wholly or partially blown with a flame from a fuel gas that comprisesa silicon-containing compound having a flash point of 0 to 100° C. and aboiling point of 105 to 250° C.

1. Solid Material

According to the first embodiment, typically, the solid material usedmay be silicone rubber or fluorine-contained rubber but details thereofwill be explained in the second embodiment.

2. Fuel Gas

(1) Silicon-Containing Compound

(i) Flash Point

It is characteristic for the flash point of the silicon-containingcompound (in closed or opened system) to be in a range between 0 and100° C.

The reason for this is that if the flash point of the silicon-containingcompound is below 0° C., the handling may be difficult in storage andthe combustion rate may be difficult to adjust. On the other hand, ifthe flash point of the silicon-containing compound exceeds 100° C., thesilicon-containing compound may have a remarkable decrease in mixingproperty with a flammable gas such as air and a combustion improver,tend to burn incompletely, and cause difficulty in exhibition of anexcellent modifying effect on a coating film made of any of variousUV-curing resins or the like.

Therefore, the flash point of the silicon-containing compound ispreferably in the range of 15 to 90° C., more preferably in the range of20 to 85° C.

Furthermore, the flash point of the silicon-containing compound may beadjusted not only restricting the structure or kind of the compounditself but also by using an appropriate mixture of thesilicon-containing compound with an alcohol compound or the like.

(ii) Boiling Point

It is characteristics for the boiling point of the silicon-containingcompound to be in a range between 105 to 250° C.

The reason for this is that if the boiling point of thesilicon-containing compound is below 105° C., the silicon-containingcompound may be strongly volatile and difficult to be handled. On theother hand, the boiling point of the silicon-containing compound exceeds250° C., the silicon-containing compound may have a remarkable decreasein mixing property with an inflammable gas such as air and a combustionimprover, tend to burn incompletely, and cause difficulty in uniformmodification of the surface of the solid material and in sustainedmodifying effect for a long time.

Therefore, the boiling point of the silicon-containing compound ispreferably in the range of 110 to 220° C., more preferably in the rangeof 120 to 200° C.

Furthermore, the boiling point of the silicon-containing compound may beadjusted not only restricting the structure or kind of the compounditself but also by using an appropriate mixture of thesilicon-containing compound with an alcohol compound or the like.

(iii) Kinds

The silicon-containing compound used contains, but not specificallylimited to, preferably at least one of a nitrogen atom, a halogen atom,a vinyl group, and an amino group in molecule or on the terminal of themolecule.

More concretely, preferable examples of the silicon-containing compoundinclude hexamethyl disilazane (boiling point: 126° C., flash point: 12to 14° C.), vinyl trimethoxysilane (boiling point: 123° C., flash point:23° C.), vinyl triethoxysilane (boiling point: 161° C., flash point: 54°C.), trifluoropropyl trimethoxysilane (boiling point: 144° C., flashpoint 23° C.), trifluoropropyl trichlorosilane (boiling point: 113 to114° C., flash point: 25° C.), 3-aminopropyl trimethoxysilane (boilingpoint: 215° C., flash point: 88° C.), 3-aminopropyl triethoxysilane(boiling point: 217° C., flash point: 98° C.), and 3-chloropropyltrimethoxysilane (boiling point: 196° C., flash point: 83° C.).

The reason of this is that such a kind of the silicon-containingcompound allows an improvement in mixing property with a flammable gasand the formation of a silica layer to more uniformly modify the surfaceof a solid material, and due to the relationship of the boiling point ofthe silicon-containing compound and the like, facilitates the compounditself to be partially remained on the surface of the solid material,thereby obtaining a more excellent adhesion strength between the solidmaterial and a coating film made of any of various UV-curing resins orthe like. In addition, the silicon-containing compound constructed asdescribed above can be provided comparatively more cheaply because offurther improvements in shelf life and ability of being filled in a gascylinder.

In addition, the silicon-containing compound that contains a nitrogenatom and a halogen atom in molecule, such as hexamethyl disilazane,trifluoropropyl trimethoxysilane, trifluoropropyl trichlorosilane,3-chloropropyltrimethoxysilane or the like has characteristic featuresof good affinity with an epoxyacrylate- or urethaneacrylate-basedUV-curing resin among other resins and easiness to exert an excellentadhesion strength to an adherend. Furthermore, the silicon-containingcompound that contains a vinyl group or an amino group on the terminalof a molecule such as vinyltrimethoxysilane, vinyltriethoxysilane,3-aminopropyl trimethoxysilane, 3-aminopropyl trietoxysilane or the likehas characteristic features of good affinity with apolyesteracrylate-based UV-curing resin in particular and is thusfacilitated to exert an excellent adhesion with the adherend.

Therefore, an excellent adhesion strength between a coating film made ofany of various UV-curing resins and an adherend can be obtained morestably by the use of a mixture of the silicon-containing compound havingnitrogen and halogen atoms and the silicon compound having vinyl andamino groups at a ratio of, for example, 10:90 to 90:10 (by weightratio).

(iv) Average Molecular Weight

It is preferable for the average molecular weight of thesilicon-containing compound to be within a range of 50 to 1,000 measuredby mass spectrum analysis.

The reason for this is that if the average molecular weight of thesilicon-containing compound is below 50, the volatility is high and thehandling becomes difficult in some cases. On the other hand, if theaverage molecular weight of the silicon-containing compound is above1,000, the evaporation by heating and the easy mixing with air and thelike becomes difficult in some cases.

Therefore, it is more preferable for the average molecular weight of thesilicon-containing compound to be within a range of 60 to 500, and it iseven more preferable for the average molecular weight of thesilicon-containing compound to be within a range of 70 to 200, measuredby mass spectrum analysis.

(v) Density

It is preferable for the density of the silicon-containing compound inliquid state to be within a range of 0.3 to 1.5 g/cm³.

The reason for this is that if the density of the silicon-containingcompound is below 0.3 g/cm³the handling becomes difficult andaccommodation in aerosol cans becomes a problem in some cases. On theother hand, if the density of the silicon-containing compound in liquidstate is above 1.5 g/cm³, the evaporation becomes difficult and in caseof accommodation in aerosol cans, a state of complete separation withthe air or the like can occur in some cases.

Therefore, it is more preferable for the density of thesilicon-containing compound to be within a range of 0.9 to 1.3 g/cm³,and it is even more preferable for the density of the silicon-containingcompound to be within a range of 0.95 to 1.2 g/cm³.

(vi) Added Amount

When the total amount of the fuel gas is 100 mol %, it is preferable forthe added amount of the silicon-containing compound to be within a rangeof 1×10⁻¹⁰ to 10 mol % of the total amount of fuel gas.

The reason for this is that if the density of the silicon-containingcompound is below 1×10⁻¹⁰ mol %, the modifying effect of solid materialsdoes not appear in some cases. On the other hand, if the density of thesilicon-containing compound is above 10 mol %, the mixing properties ofthe silicon-containing compound with air and the like decrease, leadingto imperfect combustion of the silicon-containing compound in somecases.

Therefore, when the total amount of the fuel gas is 100 mol %, it ismore preferable for the density of the silicon-containing compound to bewithin a range of 1×10⁻⁹ to 5 mol %, and it is even more preferable forthe density of the silicon-containing compound to be within a range of1×10⁻⁸ to 1 mol %.

(2) Inflammable Gas

It is preferable to add an inflammable gas or a combustible gas into thefuel gas to allow easy control of the flame temperature. Hydrocarbongases such as propane gas and natural gas, hydrogen, oxygen, air and thelike may be given as such inflammable gases or combustible gases. Incase of using inflammable gas accommodated in aerosol cans, it ispreferable to use propane gas, compressed air and the like.

When the total amount of the fuel gas is 100 mol %, it is preferable forthe contained amount of inflammable gas to be within a range of 80 to99.9 mol % of the total amount of fuel gas.

The reason for this is that if the contained amount of inflammable gasis below 80 mol %, the mixing properties of the silicon-containingcompound and air and the like decrease, leading to imperfect combustionof the silicon-containing compound in some cases. On the other hand, ifthe contained amount of inflammable gas is above 99.9 mol % , themodifying effect of solid materials does not appear in some cases.

Therefore, when the total amount of the fuel gas is 100 mol %, it ismore preferable for the contained amount of inflammable gas to be withina range of 85 to 99 mol %, and it is even more preferable for thecontained amount of inflammable gas to be within a range of 90 to 99 mol%.

(3) Carrier Gas

It is preferable to also add a carrier gas to evenly mix thesilicon-containing compound into the fuel gas. In other words, it ispreferable to premix the silicon-containing compound with a carrier gas,and to then mix it into the inflammable gas such as the air stream andthe like.

The reason for this is as follows: By adding a carrier gas, even whenusing a silicon-containing compound with a relatively high molecularweight and is difficult to transport, it may be evenly mixed into theair stream. In other words, by adding a carrier gas, thesilicon-containing compound becomes easy to burn and the surfacemodification of the solid material may be then carried out evenly andsufficiently.

As such a preferable carrier gas, it is preferable to use the same typeof gas as the inflammable gas, for example, air and oxygen.Alternatively, hydrocarbon gases such as propane gas, natural gas,andthe like may be given.

(4) Additives

(i) Kinds 1

It is preferable to add at least one compound selected from the groupconsisting of an alkylsilane compound, an alkoxysilane compound, analkyltitanium compound, an alkoxytitanium compound, an alkylaluminumcompound, and an alkoxyaluminum compound with a boiling point of below100° C. into the fuel gas as a modification enhancer.

The reason for this is as follows: By adding a modification enhancerwith excellent mutual solubility to the silicon-containing compound suchas an alkylsilane compound having a boiling point of more than 100° C.,even when using a compound with a relatively low boiling point,difficulty of the fuel gas handling due to the boiling point of thesilicon-containing compound being low may be improved and as aconsequence thereof the surface modification effect of the solidmaterial maybe further increased. Furthermore, another reason is thatthe addition of such a modification enhancer makes the adjustment offlame color easy to confirm complete burning, together with thesilicon-containing compound.

Furthermore, when the total amount of the silicon-containing compound is100 mol %, it is preferable for the added amount of the modificationenhancer to be within a range of 0.01 to 50 mol %.

The reason for this is as follows: If the added amount of thesilicon-containing compound is below 0.01 mol %, the addition effect ofthe modification enhancer does not appear in some cases. On the otherhand, if the added amount of the modification enhancer is above 50 mol%, imperfect combustion of the silicon-containing compound occurs insome cases.

Therefore, when the total amount of the silicon-containing compound is100 mol %, it is more preferable for the added amount of themodification enhancer to be within a range of 0.1 to 30 mol %, morepreferably within a range of 0.5 to 20 mol %.

(ii) Kinds 2

Furthermore, it is preferable to add an alcohol compound into the fuelgas together with the above-mentioned silicon-containing compound.

The reason for this is as follows: The alcohol compound added may beuniformly dissolved with the silicon-containing compound to facilitatethe adjustment of the boiling point and flash point of the mixturecontaining the silicon-containing compound. In addition, the addition ofsuch an alcohol compound makes the adjustment of flame color easy toconfirm complete burning, together with the silicon-containing compound.

Here, the alcohol compounds include methyl alcohol, ethyl alcohol,propyl alcohol, butyl alcohol, benzyl alcohol and the like, which may beused independently or in combination of two or more of them.

In addition, the amount of the alcohol compound added together with thesilicon-containing compound is preferably in the range of 0.01 to 30 mol% when the total amount of the silicon-containing compound is 100 mol %.

The reason of this is as follows: If the added amount of the alcoholcompound is below 0.01 mol %, the boiling point and flash point of themixture are difficult to be adjusted in some cases. On the other hand,if the added amount of the alcohol compound exceeds 30 mol %, themodifying effect on the surface of the solid material cannot be exertedin some cases.

3. Flame

(1) Temperature

It is preferable for the flame temperature to be within a range of 500to 1,500° C.

The reason for this is as follows: If the flame temperature is below500° C., it becomes difficult to prevent effectively imperfectcombustion of the silicon-containing compound in some cases. On theother hand, if the value of the flame temperature is above 1,500° C.,the solid material subject to surface modifying will be deformed ordamaged in some cases, and the types of solid materials that may be usedwill be excessively limited in some cases.

Therefore, it is more preferable for the value of the flame temperatureto be within a range of 550 to 1,200° C., and it is even more preferablefor the value of the flame temperature to be within a range of 600 to900° C.

The flame temperature may be appropriately adjusted according to thetype of fuel gas, the fuel gas throughput or the type and amount ofsilicon-containing compound added to the fuel gas.

(2) Treatment Period

It is preferable for the flame treatment period (blow period) to bewithin a range of 0.1 to 100 seconds.

The reason for this is as follows: If the value of the flame treatmentperiod is below 0.1 seconds, the modifying effect of thesilicon-containing compound does not appear evenly in some cases. On theother hand, if the value of the flame treatment period is above 100seconds, the solid material subject to surface modifying will beheat-deformed or heat-damaged in some cases, and the types of solidmaterials that may be used will be excessively limited in some cases.

Therefore, it is more preferable for the value of the flame treatmentperiod to be within a range of 0.3 to 30 seconds, and it is even morepreferable for the value of the flame treatment period to be within arange of 0.5 to 20 seconds.

4. Process of Forming Coating Film

Furthermore, for carrying out the method of modifying the surface of asolid material in accordance with the first embodiment, the method maypreferably contain a process of forming a coating film as a subsequentstep. In other words, it is preferable to form a coating film made ofUV-curing paint.

The process of forming a coating film is carried out such that a coatingfilm made of an epoxyacrylate-based UV-curing paint,urethaneacrylate-based UV-curing paint, or polyesteracrylate-basedUV-curing paint and the number of pieces of the coating film, which werepeeled off from the solid material, may be preferably 10 or less per 100grids in a cross-cut test in accordance with JISK-5400.

In other words, the conventional silicatizing flame treatment couldexert a predetermined modifying effect on one of coating films made ofepoxyacrylate-based UV-curing paint, urethaneacrylate-based UV-curingpaint, and polyesteracrylate-based UV-curing paint. However, it wasdifficult to exert the predetermined effect on all of the coating films.Therefore, in the first embodiment, the method for modifying the surfaceof a solid material further includes the step of forming a coating film.The method can be quantitatively performed in a reliable manner byclarifying the standard of the predetermined modifying effect bydetermining the number of pieces of the coating film, which are peeledoff, by the cross-cut test in accordance with JIS K-5400.

By the way, the epoxyacrylate-based UV-curing paint is preferablyUV-curing paint basically constructed of an epoxy acrylate oligomerhaving a polar group such as a phosphate group and the like, an acrylatemonomer, and a curing agent.

In addition, the urethaneacrylate-based UV-curing paint is preferablyUV-curing paint basically constructed of an urethane acrylate oligomer,an acrylate monomer, and a curing agent.

Furthermore, the polyetsteracrylate-based UV-curing paint is preferablyUV-curing paint basically constructed of a polyester acrylate oligomer,an acrylate monomer, and a curing agent.

Second Embodiment

The second embodiment is a surface-modified solid material having awetting index of 40 to 80 dyn/cm (measuring temperature 25° C.) attainedby subjecting the surface of the solid material wholly or partially to ablow treatment with a flame of a fuel gas that comprises asilicon-containing compound having a flash point of 0 to 100° C. and aboiling point of 105 to 250° C.

1. Solid Material

(1) Rubber

Furthermore, for constructing the surface-modified solid material, thesolid material may be at least one of rubber types selected from thegroup consisting of: silicone rubber, fluorine-contained rubber, naturalrubber, neoprene rubber, chloroprene rubber, urethane rubber, acrylrubber, olefin rubber, styrene-butadiene rubber, acrylonitrile-butadienerubber, ethylene-propylene rubber, ethylene-propylenediene rubber,butadiene rubber, butyl rubber, styrene type thermoplastic elastomer,and urethane type thermoplastic elastomer.

Among these rubber types, an excellent modifying effect may be obtainedaccording to the surface modification of the present invention withlarge wetting angle of contact, low wetting index silicone rubber,fluorine-contained rubber, olefin rubber, ethylene-propylene rubber.Therefore, it becomes easy to print numbers, letters, and the like onthe surface of stain-proof rubber and dirt covers such as siliconerubber and fluorine-contained rubber.

(2) Resin

Furthermore, for constructing the surface-modified solid material,examples of the solid material may include: a polyethylene resin (highdensity polyethylene, medium density polyethylene, low densitypolyethylene, high pressure polyethylene, medium pressure polyethylene,low pressure polyethylene, linear low density polyethylene, branch lowdensity polyethylene, high pressure linear low density polyethylene,super molecular weight polyethylene, cross-linked polyethylene),polypropylene resin, denatured polypropylene resin, polymethyl penteneresin, polyester resin, polycarbonate resin, polyether sulfone resin,polyacryl resin, polyether ether ketone resin, polyimide resin,polysulfone resin, polystyrene resin, polyamide resin, and polyphenylensulfide resin, ethylene-tetrafluoroethylen copolymer, polyvinyl fluorideresin, atetrafluoroethylene-perfluoroether copolymer,tetrafluoroethylene-hexafluoropropylene copolymer,polytetrafluoroethylene resin, polyvinylidene fluoride resin,polytrifluorochloroethylene resin, and ethylene-trifluorochloroethylenecopolymer.

Among these resin types an excellent modifying effect may be obtainedaccording to the surface modification of the present invention withlarge wetting angle of contact, a low wetting index polyethylene resin,polypropylene resin, polyester resin, polycarbonate resin,polytetrafluoroethylene resin, and the like.

Therefore, the printing of letters and patterns onto films made of apolyethylene resin or a polypropylene resin, or onto receptacles made ofpolyester, the firm adhering of aluminum reflecting film to compact diskboards made of a polycarbonate resin and also the printing of numbers,letters, and the like onto dirt-repellent material made of apolytetrafluoroethylen resin become possible.

(3) Thermosetting Resins

Furthermore, for constructing the surface-modified solid material, otherexamples of the solid material may include an epoxy resin, a phenolresin, a cyanate resin, an urea resin, and a guanamine resin. Amongthese thermosetting resins, in case of an epoxy resin for example,laser-marking on semiconductor plastic encapsulation resins may becarried out easily according to the surface modification of the presentinvention.

(4) Metal Materials

Furthermore, for constructing the surface-modified solid material, otherexamples of the solid material may include metal materials such asaluminum, magnesium, stainless steel, nickel, chromium, tungsten, gold,copper, iron, silver, zinc, tin, and lead, which may be usedindependently or in combination of two or more of them.

For instance, aluminum is widely used as a light metal, but showsseveral problems in that it tends to form a surface oxidation layer,which facilitates peeling-off of UV curing paint or the like even whenapplied directly. Now, by carrying out silicatizing flame treatment orthe like on the aluminum surface, the peeling-off of UV curing paint orthe like even when applied directly may be effectively prevented.

Further, magnesium as a recyclable metal is widely used in recent yearsin personal computer bodies and son on, but shows the problems of easypeeling-off (detachment) of UV curing paint and the like even whenapplied directly due to poor surface smoothness. Now, by carrying outsilicatizing flame treatment or the like on the magnesium surface, thepeeling-off (detachment) of UV curing paint or the like even whenapplied directly may be effectively prevented and colored magnesiumsheets or the like may be then provided.

Further, currently, when gold bumps or solder bumps of semiconductorelements are electrically connected to film carrier and circuit board ina high temperature and high moisture environment, problems appear withoccurring surface detachment. Now, by carrying out silicatizing flametreatment or the like on either the gold bumps or solder bumps, or thefilm carrier or circuit board, the surface detachment may be effectivelyprevented.

Further, the silicatizing flame treatment is a treatment using a flamethat comprises a silicon-containing compound which enables the formingof a silicon oxide layer on the whole substrate substance or on part ofit by blazing heat decomposition of the substrate substance.

(5) Inorganic Materials Other than Metal Materials

Preferable inorganic materials other than metal materials, which - canconstitute the solid materials of the invention, include titanium oxide,zirconium oxide, zinc oxide, indium oxide, tin oxide, silica, talc,calcium carbonate, lime, zeolite, glass, and ceramic, which may be usedindependently or in combination of two or more of them.

(6) Form

Exemplified forms of the solid material to be subjected to the treatmentinclude, but not specifically limited to, those having plane structures,such as a board shape (a plate shape), a sheet shape, a film shape, atape shape, a strip shape, a panel shape, and a strap shape, as well asthose having three-dimensional structures, such as a cylinder shape, acolumn shape, a sphere shape, a block shape, a tube shape, a pipe shape,a concavo-convex shape, a membrane shape, a fiber shape, a fabricsshape, and a bundle shape.

For example, by carrying out silicatizing flame treatment or the like onfiber glass or carbon fiber, the surface thereof may be modified andactivated, and the fibers may be distributed evenly in a matrix resinsuch as epoxy resin and a polyester resin. Therefore, excellentmechanical strength, heat resistance and the like may be achieved in FRPand CFRP.

Further, as such a form of matter subject to treatment, it is alsopreferable for it to be of a composite structure such as of a solidmaterial combined with a metal part, ceramic part, glass part, paperpart, wooden part, and the like.

For example, by carrying out silicatizing flame treatment and the likeon the inner side of a metal pipe or a ceramic pipe, the surface ismodified and activated and a layered pipe with an extremely strong resinliner may be obtained.

Further, by carrying out silicatizing flame treatment and the likewholly or in part of the surface of a board, that is a plastic board orglass board, such as a liquid crystal display device, organic electroluminescence device, plasma display device, or a CRT, an organic filmsuch as a color filter, a deflection sheet, a light scattering sheet, ablack matrix sheet, an anti-reflection film, or an anti-static film maybe laminated extremely evenly and firmly.

2. Fuel Gas

The description is omitted here because the same silicon-containingcompounds and inflammable gases as those described in the firstembodiment may be used in the present embodiment.

3. Flame

The description is omitted here because the same flame temperatures andtreatment periods as those described in the first embodiment may be usedin the present embodiment.

4. Wetting Index (Surface Energy)

(1) After Surface Modification

Further, it is preferable for the wetting index of the surface-modifiedsolid material to be in a range between 40 and 80 dyn/cm (measuringtemperature 25° C.).

The reason for this is that if the value of the wetting index of thesolid material is below 40 dyn/cm, easy adhesion, printing, painting andthe like becomes difficult in some cases. On the other hand, if thevalue of the wetting index of the solid material is above 80 dyn/cm, thesurface treatment is overly carried out and the solid material isheat-damaged in some cases.

Therefore, it is more preferable for the value of the wetting index ofthe surface-modified solid material to be in a range between 45 and 75dyn/cm, and it is even more preferable for the value to be in a rangebetween 50 and 70 dyn/cm.

Here, the wetting index (dyn/cm) of the solid material before thesurface modification and the wetting index (dyn/cm) of the solidmaterial after the surface modification (for 0.5 seconds) were measuredusing a standard solution at 25° C. The results of the measurements arelisted as measurement examples in Table 1.

(2) Before Surface Modification

Further, it is preferable for the value of the wetting index of thesolid material before surface modification (before surface treatment) tobe in a range between 20 and 45 dyn/cm (measuring temperature 25° C.).

The reason for this is that if the wetting index of the solid materialis below 20 dyn/cm, the surface treatment needs to be carried out over along period, so that the solid material is heat-damaged in some cases.On the other hand, if the value of the wetting index of the solidmaterial is above 45 dyn/cm, efficient surface treatment by flamebecomes difficult in some cases. For example, the wetting index ofpolyethylene resin before modification treatment is about 40 dyn/cm, andalthough it also depends on the silicatizing flame treatment temperatureand the like, with about 1 second of silicatizing flame treatment, thewetting index may be increased to about 60 dyn/cm or more.

Therefore, it is more preferable for the value of the wetting index ofthe solid material before surface modification (before surfacetreatment) to be in a range between 25 and 38 dyn/cm (measuringtemperature: 25° C.), and it is even more preferable for the value to bein a range between 28 and 36 dyn/cm.

5. Contact Angle

(1) After Surface Modification

Further, it is preferable for the contact angle of the surface-modifiedsolid material, measured using water, to be in a range between 0.1 and30° (measuring temperature: 25° C.).

The reason for this is that if the value of the contact angle of thesolid material is below 0.1°, the surface treatment is overly carriedout, so that the solid material is heat-damaged in some cases. On theother hand, if the value of the contact angle of the solid material isabove 30°, easy adhesion, printing, painting, and the like becomesdifficult in some cases.

Therefore, it is more preferable for the value of the contact angle ofthe surface-modified solid material, measured using water, to be in arange between 0.5 and 20° (measuring temperature 25° C.), and it is evenmore preferable for the value to be in a range between 1 and 100.

(2) Before Surface Modification

Further, it is preferable for the value of the contact angle, measuredusing water, of the solid material before surface modification (beforesurface treatment) to be in a range between 50 and 120° (measuringtemperature: 25° C.).

The reason for this is that if the contact angle of the solid materialis below 50°, efficient surface treatment by flame becomes difficult insome cases. On the other hand, if the value of the contact angle of thesolid material is above 120°, the surface treatment needs to be carriedout over a long period of time, so that the solid material isheat-damaged in some cases. For example, the contact angle ofpolytetrafluoroethylene resin before modification treatment is about108°, and although it also depends on the silicatizing flame treatmenttemperature and the like, with about 1 second of silicatizing flametreatment, the contact angle may be decreased to approximately below20°.

Therefore, it is more preferable for the value of the contact angle ofthe solid material before surface modification (before surfacetreatment), measured using water, to be in a range between 60 and 110°,and it is even more preferable for the value to be in a range between 80and 100°.

6. Coating Film

The surface of the solid material subjected to the predeterminedsilicatizing flame treatment is preferably provided with any of coatingfilms (about 5 to 500 μm in thickness) consisting of epoxyacrylate-basedUV-curing paint, urethaneacrylate-based UV-curing paint, andpolyesteracrylate-based UV-curing paint.

The reason of this is that the solid material of the second embodimentdoes not require any strict selection of the kind of paint, the coatingfilm having an excellent adhesion strength can be formed by a UV-curingtreatment on the solid material, and hence the commercial value or thelike of the solid material can be enhanced quickly at a low price.

Third Embodiment

The third embodiment is an apparatus 10 for modifying a surface of asolid material, as shown in FIG. 1, containing a storage tank 12 forstoring a silicon-containing compound 14 having a flash point of 0 to100° C. and a boiling point of 105 to 250° C., a transfer part 24 fortransferring the fuel gas and an outlet part 32 for letting out the fuelgas flame 34 for blow treatment.

1. Storage Tank

As shown in FIG. 1, preferably, the storage tank may comprise a firststorage tank 12 having a heating device 16, for storing thesilicon-containing compound 14, and a second storage tank (not shown)for storing an inflammable gas such as compressed air and the like. Inthis example, the heating device 16 is mounted on the bottom part of thefirst storage tank 12. The heating device 16 may comprise a heater and aheat transfer line, or may comprise a heating board or the like that isconnected to a heat exchanger, for evaporating the silicon-containingcompound 14 in a liquid state at ambient temperature and atmosphericpressure.

When the solid material is surface-treated, it is preferable for thesilicon-containing compound 14 in the first storage tank 12 to be heatedby the heating device 16 to a predetermined temperature, and inevaporated state to be mixed with the inflammable gas (e.g., air) toform the fuel gas.

Furthermore, because the amount of silicon-containing compound includedin the fuel gas is of extreme importance, the amount of thissilicon-containing compound should also be indirectly controlled. It istherefore preferable to monitor the silicon-containing compound's steampressure (or the silicon-containing compound amount) by providing apressure gauge (or a liquid surface level gauge) 18 in the first storagetank 12.

2. Transfer Part

The transfer part is usually a pipe structure, and as shown in FIG. 1,preferably contains a mixing chamber 22 for forming the fuel gas byevenly mixing the silicon-containing compound 14 transferred from thefirst storage tank 12 and the inflammable gas (air) transferred from thesecond storage tank (not shown), as well as a valve and throughput gaugeto control the throughput, or a pressure gauge 28 to control the fuelgas pressure.

Further to mixing the silicon-containing compound and inflammable gasevenly, a mixing pump in the mixing chamber 22 in order to strictlycontrol the throughput and an obstruction board or the like to prolongthe retention period are preferably included.

3. Outlet Part

(1) Structure

The outlet part, as shown in FIG. 1, preferably comprises a burner 32for blow treatment of the solid material subjected to treatment with aflame 34 obtained by burning the fuel gas transferred from the transferpart 24. Exemplified types of the burner include, but not specificallylimited to, a premixing type burner, a diffusion type burner, apartial-premixing type burner, a spraying burner, an evaporation burner,a pulverized coal burner and the like. Further, the form of the burnermay be, but not specifically limited to, as shown in FIG. 1, a fan-typeas a whole spreading toward the tip portion, or as shown in FIG. 4, theform of the burner may be a rectangle with jet nozzles 64 being alignedalong the lateral sides.

(2) Arrangement

It is preferable to determine the arrangement of the outlet part, Inother words, the layout of the burner taking into consideration the easeof surface modification of the solid material subject to treatment.

For example, it is preferable to arrange it along a circular orelliptical shape as shown in FIG. 2, but it is also preferable toarrange it adjacent to both sides of a solid material subject totreatment as shown in FIG. 4.

Further, it is also preferable to arrange it at a prescribed distancefrom one of the sides of a solid material subject to treatment as shownin FIG. 5 a, but it is also preferable to arrange it at a prescribeddistance each from both sides of a solid material subject to treatmentas shown in FIG. 5 b.

4. Form

(1) Stationary Type

The apparatus for modifying a surface of a solid material preferablycomprises, for example, as shown in FIG. 1, a storing tank 12, atransfer part 24 for transferring the fuel gas, and an outlet part 32for blow treatment with a flame obtained from the fuel gas, and therespective parts are installed. As shown in FIG. 2, the solid material,mounted on a fixing jig 38 on a rotation table 36, is preferably blowtreated with a flame 34 from the outlet part 32 with changing itsposition of the solid material subject to treatment and rotating thesolid material by the fixing jig 38.

According to the stationary type of apparatus 10 for modifying thesurface of the solid material, the surface of the solid material subjectto treatment may be modified in large scale and efficiency.

(2) Portable Type

The apparatus for modifying a surface of a solid material 42 ispreferably a portable type as shown in FIG. 3. That is, as shown in theregion surrounded by the dotted lines, the apparatus comprises acartridge-type storing tank 46, a laying pipe 47, a box 44 provided witha throughput gauge and a pressure gauge, wherein the laying pipe 47comprises a burner 32 in its tip portion. According to the aboveconstruction, by transferring the box 44 timely, both the solidsubstance subject to treatment being placed outdoors and the solidsubstance subject to treatment having a large size and capacity may besurface modified easily.

In order to carry the box easily, the box 44 is preferably provided witha handle or a cord on its upper portion, and the weight of the box 44 ispreferably 20 kg or less.

5. UV-Irradiation Apparatus

A UV-irradiation apparatus may preferably be provided in theneighborhood of or in parallel with the apparatus for modifying thesurface of a solid material. In other words, the UV-irradiationapparatus quickly forms any of coating films made of anepoxyacrylate-based UV-curing paint, an urethaneacrylate-based UV-curingpaint, and polyesteracrylate-based UV-curing paint onto the surface of asolid material subjected to the predetermined silicatizing flametreatment without any strict selection of the kind of target paint.

EXAMPLE 1

1. Surface Modification of a Solid material

An aluminum plate having a thickness of 2 mm (A1 plate, 10 cm×5 cm) anda polypropylene resin plate having a thickness of 2 mm (PP plate, 10cm×5 cm) were prepared, respectively. Then, each of these plates wassubjected to a silicatizing treatment for 0.2 seconds per unit area (50cm²) using a portable surface-modifying apparatus shown in FIG. 3.

As a fuel gas, a mixed gas containing 0.01 mol % of hexamethyldisilazane and the remainder, 99.99 mol % of compressed air, in acartridge was used.

2. Evaluation of Solid Material

(1) Wetting Index

The wetting index of a surface modified plate was measured using astandard liquid. Further, the wetting index of the plate before surfacemodification was measured in the same way.

(2) UV Paint Properties

After screen-printing an epoxyacrylate-based UV-curing paint (Type 1),urethaneacrylate-based UV-curing paint (Type 2), andpolyesteracrylate-baed UV-curing paint (Type 3) onto the respectivesurface-modified plates, 300 mJ/cm² of UV rays were irradiated with anUV irradiation apparatus and then evaluated on the basis of thefollowing criteria, while the UV paint properties to the respectiveplates before surface modification were also measured in the same way:

-   Very good: According to the cross-cut adhesion test of 100 pieces    (JIS Standard), no piece was peeled off.-   Good: According to the cross-cut adhesion test of 100 pieces (JIS    Standard), 1 or 2 piece(s) was(were) peeled off.-   Fair: According to the cross-cut adhesion test of 100 pieces (JIS    Standard), 3 to 10 pieces were peeled off.-   Bad: According to the cross-cut adhesion test of 100 pieces (JIS    Standard), more than 11 pieces were peeled off.

EXAMPLES 2 TO 7

In Examples 2 to 7, as shown in Table 1, surface-modified solidmaterials with different modifying agents were evaluated in the same wayas that of Example 1.

COMPARISON EXAMPLE 1

The surface of a solid material was modified and the evaluation of thesolid material was then carried out just as in the case with comparisonexample 1, excepting that a mixed gas of compressed air withhexamethyldisiloxane was used instead of the mixed gas of compressed airwith hexamethyldisilazane of Example 1. TABLE 1 Wetting index (dyn/cm)UV-paint Solid Modifying Before After properties material agenttreatment treatment Type 1 Type 2 Type 3 Example 1 Al HMDN 34 >72 veryvery good good good PP 30 >72 very very good good good Example 2 Al VTMS34 >72 fair good very good PP 30 >72 fair very very good good Example 3Al TFTM 34 >72 very very good good good PP 30 >72 very very good goodgood Example 4 Al ClTM 34 >72 very very good good good PP 30 >72 verygood good good Example 5 Al HMDN/ 34 >72 very very good ETA good good PP30 >72 very very good good good Comparative Al HMDS 34 >72 bad fair goodExample 1 PP 30 >72 bad fair good Comparative Al TMS 34 >72 bad fairgood Example 2 PP 30 >72 bad fair good*HMDN: hexamethyldisilazane*VTMS: vinyltrimethoxysilane*HMDN/ETA: hexamethyldisilazane/ethanol*TFTM: trifluoropropyl trimethoxysilane*ClTM: 3-chloropropyl trimethoxysilane*HMDS: hexamethyldisiloxane

EXAMPLES 6 TO 7 AND COMPARATIVE EXAMPLES 3 TO 4

In Example 6, a silicatizing flame treatment using hexamethyldisilazane(HMDN) was carried out in the same way as that of Example 1 and thensubjected to evaluation of the wetting index and UV-paint property (Type2), while the rest period was changed to 2 weeks and to 4 weeks,respectively.

In Examples 7 and 8, a silicatizing flame treatment was carried out inthe same way as that of Example 6, excepting that trifluoropropyltrimethoxysilane (TFTM) and 3-chloropropyl trimethoxysilane (ClTM) wereused instead of hexamethyldisilazane. Subsequently, the wetting indexand UV-paint property (Type 2) were evaluated, while the rest period waschanged in the same way as that of Example 6.

Furthermore, in Comparative Example 3, after carrying out a silicatizingflame treatment using hexamethyldisiloxane, the wetting index andUV-paint property (Type 2) were evaluated, while the rest period waschanged in the same way as that of Example 6. Furthermore, inComparative Example 4, a corona treatment was carried out instead of thesilicatizing flame treatment. Subsequently, the wetting index andUV-paint property (Type 2) were evaluated, while the rest period waschanged in the same way as that of Example 6. TABLE 2 Wetting UV paintindex property Solid Modification (dyn/cm) (Type 2) material treatment 2week 4 week 2 week 4 week Example 6 PP HMDN 70 70 very good 0.2 secondsgood Example 7 PP TFTM 70 70 very very 0.2 seconds good good Example 8PP ClTM 70 70 good good 0.2 seconds Com- PP HMDS 60 57 very fairparative 0.2 seconds good Example 3 Com- PP Corona 30 30 bad badparative treatment/ Example 4 60 seconds

INDUSTRIAL APPLICABILITY

As stated above, according to the method for modifying the surface of asolid material in connection with the present invention, a silicatizingflame treatment is carried out by blowing a flame of a fuel gascontaining a specific silicon-containing compound onto the solidmaterial. Therefore, the surface-modification method for the solidmaterial, which is capable of exerting an excellent modifying effecteven on any of coating films made of various UV-curing resins and so on,and a surface-modified solid material can be obtained.

Accordingly, it becomes possible to form any of coating films made ofvarious UV-curing resins and soon, which had been impossible in the art,on the surface-modified solid material of the invention, for example,even on the representative poorly adhesion materials including siliconerubber, fluorine-contained rubber, olefin resin, and polyester resin, aswell as metals such as stainless steel, magnesium or the like.

1. A method for modifying a surface of a solid material, comprising:carrying out a silicatizing treatment on the surface of the solidmaterial by wholly or partially blowing a flame of a fuel gas thatcontains a silicon-containing compound having a flash point of 0 to 100°C. and a boiling point of 105 to 250° C. onto the surface of the solidmaterial.
 2. The method according to claim 1, wherein thesilicon-containing compound has at least one of a nitrogen atom, ahalogen atom, a vinyl group, and an amino group in molecule or on aterminal of the molecule.
 3. The method according to claim 1, whereinthe silicon-containing compound is selected from the group consisting ofhexamethyldisilazane, vinyltrimethoxysilane, vinyltriethoxysilane,trifuloropropyl trimethoxysilane, trifluoropropyl trichlorosilane,3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and3-chloropropyl trimethoxysilane, which is used independently or incombination of two or more of them.
 4. The method according to claim 1,wherein the silicon-containing compound is a mixture of asilicon-containing compound containing a nitrogen atom and a halogenatom in molecule with a silicon-containing compound containing a vinylgroup or an amino group on the terminal of the molecule.
 5. The methodaccording to claim 1, further comprising: adding an alcohol compound tothe silicon-containing compound, wherein the amount of the alcoholcompound added is in the range of 0.01 to 30 mol % when the total amountof the silicon-containing compound is defined as 100 mol %.
 6. Themethod according to claim 1, wherein the content of thesilicon-containing compound in the fuel gas is in the range of 1×10⁻¹⁰to 10 mol % when the total amount of the fuel gas is defined as 100 mol%.
 7. The method according to claim 1, wherein the silicon-containingcompound is in a vapor-liquid equilibrium state, and a gaseous part ofthe silicon-containing compound is mixed in the fuel gas and thencombusted.
 8. The method according to claim 1, further comprising: aUV-curing step as a step subsequent to the step of modifying the surfaceof the solid material, wherein a coating film made of UV-curing paint isformed on a surface-modified solid material.
 9. The method according toclaim 8, wherein, in a cross-cut adhesion test in accordance with JISK-5400, the number of pieces of the coating film made of any ofepoxyacrylate-based UV-curing paint, urethaneacrylate-based UV-curingpaint, and polyesteracrylate-based UV-curing paint, which are peeled offfrom their corresponding grids, is 10 or less per 100 grids.
 10. Asurface-modified solid material, having a wetting index of 40 to 80dyn/cm (measured at 25° C.) obtained by carrying out a silicatizingflame treatment on a surface of a solid material by wholly or partiallyblowing a flame of a fuel gas that contains a silicon-containingcompound having a flash point of 0 to 100° C. and a boiling point of 105to 250° C. onto the surface of the solid material.
 11. Thesurface-modified solid material according to claim 10, wherein thewetting index of the solid material before the surface treatment is inthe range of 20 to 45 dyn/cm (measured at 25° C.).
 12. Thesurface-modified solid material according to claim 10, wherein a coatingfilm made of UV-curing paint is formed on the surface-modified material.